Use of compost in potting soils

Leaf compost can be used as a component of potting mixes. Generally, no more than one-quarter to one-third by volume of the potting mix should be compost, because over time some of the compost is likely to decompose and the volume of the potting soil will be reduced. In addition, high levels of compost in a potting mix may cause waterlogging and poor aeration for roots.

Although proper composting destroys most weed seeds and disease organisms, some may still survive due to incomplete mixing. To obtain a completely pasteurized leaf compost, it is necessary to heat the material in an oven until the temperature of all the material reaches 160 degrees F and is maintained for 30 minutes or longer. Pasteurization will also kill beneficial organisms in compost, some of which help to suppress certain soilborne diseases. So if your compost doesn't have many weed seeds or disease organisms, there may be an advantage to using it unpasteurized fresh.